Abstract

Background

A school-based physical activity intervention designed to encourage adolescent girls
to be more active was more effective for some participants than for others. We examined
whether baseline enjoyment of exercise moderated response to the intervention.

Methods

Adolescent girls with a low level of baseline activity who participated in a controlled
trial of an intervention to promote increased physical activity participation (n = 122) self-reported their enjoyment of exercise and physical activity participation
at baseline, mid-way through the intervention, and at the end of the 9-month intervention
period. At all three time points, participants also underwent assessments of cardiovascular
fitness (VO2peak) and body composition (percent body fat). Repeated measures analysis of variance
examined the relationship of baseline enjoyment to change in physical activity, cardiovascular
fitness, body composition and enjoyment of exercise.

Results

A significant three-way interaction between time, baseline enjoyment, and group assignment
(p < .01) showed that baseline enjoyment moderated the effect of the intervention
on vigorous activity. Within the intervention group, girls with low enjoyment of exercise
at baseline increased vigorous activity from pre-to post-intervention, and girls with
high baseline enjoyment of exercise showed no pre-post change in vigorous activity.
No differences emerged in the comparison group between low-and high-enjoyment girls.

Conclusion

Adolescent girls responded differently to a physical activity promotion intervention
depending on their baseline levels of exercise enjoyment. Girls with low enjoyment
of exercise may benefit most from a physical-education based intervention to increase
physical activity that targets identified barriers to physical activity among low-active
adolescent girls.